In the current and conventional plastic lighter, a sponge rod is usually mounted in a transparent gas reservoir to form a gas-flow passage to connect the gas flow system and the gas regulating system. The gas regulating system includes a flame adjuster with inner ratchet teeth to be mounted around a valve member. Whenever the flame adjuster is turned, the valve member will be moved upwards or downwards so as to control the flow of gas. The gas ignition system includes a pressing plate to control the flow of gas. A fire-striking wheel can be rotated to ignite the gas flowing out. The aforesaid structure has been used for over ten years without any major change. However, it has some drawbacks, such as: a complicated structure, which requires it to be assembled through complicated steps; and it has incomplete functions and poor ignition efficiency. In view of the aforesaid drawbacks, the lighter according to the present invention has been improved: (1) to simplify the gas flow system; (2) to simply the gas regulating system to improve its function; and (3) to improve the gas ignition system with better ignition efficiency. Since the number of parts of the present invention have been reduced, the assembling operation for the lighter will be considerably improved.